In four-stroke internal combustion engines, in order to control the charge change, poppet valves may be used. The poppet valves are movable along their longitudinal axis between a valve closing position and a valve opening position. During operation of an internal combustion engine, the poppet valves execute an oscillating stroke motion in order to open or close inlet and outlet openings of cylinders of the engine.
An actuating device of a poppet valve is often referred to as a valve train. The valve train may oscillate the poppet valve to open and close the corresponding inlet or outlet opening of the cylinder to which the poppet valve is coupled. A valve spring may be provided in order to preload the poppet valve in a direction of the valve closing position, and the valve-actuating device or valve train is provided in order to open the valve, opposite to a preload force of the valve spring. Often, the valve train comprises a camshaft with a cam, with at least one cam follower element disposed between the cam and the poppet valve.
Attempts to address coupling the poppet valve to the valve spring and valve train include providing fasteners to join the components to each other. One example approach is shown in European Patent 1 741 881 B1. Therein, a valve spring retainer is formed integrally with intermediate elements of a valve train.
However, the inventors herein have recognized potential issues with such systems. As one example, fasteners or valve spring retainers such as those disclosed by the '881 patent may increase a weight of the valve spring, poppet valve, and/or valve train, which may result in a decreased responsiveness of the poppet valve. Further, such fasteners or valve spring retainers may increase a cost and/or assembly time of the engine.
In one example, the issues described above may be addressed by an internal combustion engine, comprising: at least one cylinder head comprising at least one cylinder, where each cylinder has at least one outlet opening for discharging exhaust gases via an exhaust gas discharge system and at least one inlet opening for supplying fresh air via an intake system, where, for each outlet and inlet opening, a poppet valve of a valve train and a valve-actuating device included with a camshaft is provided for actuating the poppet valve, and where each poppet valve has a valve stem on a cylinder-side end, facing the at least one cylinder where a valve retainer corresponding to the at least one outlet opening or at least one inlet opening is arranged, and where each poppet valve has an end on a valve train side which faces the valve-actuating device, with each poppet valve mounted so as to be translationally movable in a corresponding sleeve-like valve stem guide so that on actuation and with the camshaft rotating, each poppet valve executes an oscillating stroke movement in a direction of its longitudinal axis between a valve closing position and a valve opening position in order to open and block the corresponding outlet or inlet opening, wherein each poppet valve includes a coil spring as a valve spring which pretensions the poppet valve in a direction of the valve closing position; and wherein each coil spring comprises several windings and rests on a cylinder side on the at least one cylinder head and on the valve train side on the valve stem, wherein a groove is provided running around the valve stem, wherein the last winding of the coil spring on the valve train side engages the groove, so that a form-fit connection is created between the valve stem and the last winding. In this way, a number of fasteners or other separate components used to operate the poppet valve may be reduced, which may reduce a weight and/or cost of the poppet valve and/or increase engine performance.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.